1. Field of the Invention
This invention relates to integrated circuit (IC) packaging technology, and more particularly, to a method of fabricating a BGA (Ball Grid Array) IC package of the type having an encapsulating body, which allows the BGA IC package to be manufactured without having to use conventional organic substrate and encapsulating-body mold having cavity, so that the manufacture process can be more cost-effective to carry out than the prior art.
2. Description of Related Art
The BGA IC packaging technology allows an IC package to be made very small in size while nevertheless providing highly integrated functionality from a single IC package. A conventional method for fabricating a BGA IC package of the type having an encapsulating body is disclosed in U.S. Pat. No. 5,830,800, whose procedural steps are briefly depicted in the following with reference to FIGS. 1A-1F.
Referring to FIG. 1A, in the first step, a copper sheet 10 is prepared. Next, a dry film 20 of a predetermined pattern is formed over the copper sheet 10. The dry film 20 can be formed by, for example, first coating a photoresist layer over the copper sheet 10, and then removing selected portions of the photoresist layer through a masked exposure/development/etching process.
Referring to FIG. 1B, in the next step, an electrically-conductive material is coated over those areas over the copper sheet 10 that are unmasked by the dry film 20 to thereby form an electrically-conductive trace structure 30 over the copper sheet 10. After this, the entire dry film 20 (FIG. 1A) is removed. Subsequently, an IC chip 40 is mounted over the electrically-conductive trace structure 30.
Referring to FIG. 1C, in the next step, a wire-bonding process is performed to apply a set of bonding wires 50 for electrically coupling the IC chip 40 to corresponding I/O ports on the electrically-conductive trace structure 30.
Referring to FIG. 1D, in the next step, an encapsulating body 60 is formed to encapsulate the IC chip 40, the bonding wires 50, and the electrically-conductive trace structure 30.
Referring to FIG. 1E, in the next step, the copper sheet 10 is removed through an etching process. After the copper sheet 10 is removed, the bottom side of the electrically-conductive trace structure 30 is exposed.
Referring to FIG. 1F, in the next step, an anti-oxidation coating 70 is formed over the bottom side of the encapsulating body 60, while uncovering the electrically-conductive trace structure 30. After this, a plurality of solder balls 80 are bonded to corresponding points on the electrically-conductive trace structure 30. This completes the BGA IC package fabrication.
The foregoing patented method has the benefit of allowing the overall manufacture process to be simplified without having to use thick organic substrate, so that is highly cost-effective to carry out. For this reason, it is suitable for use to manufacture those IC packages that are to be mounted on small computers and intelligent electronic devices, such as palmtop computers and mobile phones.
One drawback to the forgoing patented method, however, is that it is only suitable for fan-out design, making the overall size difficult to be further reduced. This is because that the electrically-conductive trace structure 30 can be formed only beyond, and not within, the junction region of the IC chip 40, making the surface area of the overall package body quite large. Still one drawback is that the etching process required to remove the copper sheet 10, if not precisely controlled, would easily cause surface damage to the bottom side of the electrically-conductive trace structure 30 and the encapsulating body 60, which would undesirably degrade the quality of the resulted BGA IC package. Moreover, after the copper sheet 10 is removed, the bottom side of the semi-finished package configuration is only supported by the electrically-conductive trace structure 30, which is considered weak, thus making the positioning of the solder balls on the electrically-conductive trace structure 30 quite difficult to carry out.